Some storage subsystems or disk array systems include storage devices such as hard disk drives and storage controllers for controlling data input/output processing for the storage devices. As an example of this type of storage subsystem or disk array systems, one having host interfaces for transmitting/receiving information to/from host computers, hard disk drive interfaces for transmitting/receiving information to/from hard disk drives, processing units for processing data according to commands from the host computers, cache memories for temporarily storing data to be sent to/from the hard disk drives, and switches mutually connecting the respective units, in which these units are installed in dedicated packages respectively and each package is configured using a dedicated LSI (Large Scale Integrated circuit) (refer to Patent Literature 1) has been proposed.
If each unit in a storage subsystem is configured as a dedicated package, even in case the storage subsystem is made in a redundant configuration or the storage subsystem is made in a small-scale configuration, a medium-scale configuration, or a large-scale configuration, the storage subsystem can be configured according to the scale by adding dedicated packages.